1. Field of the Invention
The present invention relates to a scalable fish rearing raceway system and method of making same. More particularly, the present invention relates to a new and improved scalable fish rearing raceway system including a greatly increased fish culture zone, unique fish harvesting/grading channel component, and integrated monitoring and feeding means which greatly reduces direct labor associated with all aspects of the fish rearing process.
2. Description of the Related Art
As health conscious Americans begin to consume more fish products and the naturally occurring sources of fish become depleted, there is a growing need to fill the demand for fish products by turning to aquaculture. Aquaculture is defined as the production and husbandry of aquatic plants and animals in controlled environments. The term husbandry means the application of scientific principles to farming. Controlled environments are directed or regulated production environments ranging from a low level of control, termed “extensive,” where limited capital and management are applied, to a high level of control, termed “intensive,” where more comprehensive capital and management are applied to production.
Aquaculture has become a one billion dollar industry in the U.S. Nearly 30% of our edible seafood supplies are currently supplied by aquaculture. Growing at a rate of 20% per year, aquaculture is the fastest growing sector of the agriculture industry. Aquaculture is an ecologically efficient means of providing seafood for American consumers while significantly reducing pressure on our limited wild fisheries resources.
Foreign competition is having a major impact on U.S. aquaculture operations. More than 60% of our seafood supplies are now imported, resulting in a large annual trade deficit ($6.9 billion). A growing fraction of aquaculture imports comes from the warm climates of South America and Asia. These countries have the advantage of lower production costs by using abundant quantities of warm water that are available in the tropics. Often there are few or no environmental laws controlling their discharges which result in environmental degradation and little or no overhead costs associated with complying with environmental laws. Imports of fish grown in Chili, Costa Rica, Ecuador, Taiwan, China, Vietnam and Indonesia have increased markedly as the foreign competition adopts new culture technologies, often developed here in the U.S. These competing products are produced with low energy, water, labor, and environmental costs. As a result, many U.S. aquaculture products are not competitive with foreign aquaculture products.
Efficient, economical and productive aquaculture in the United States would meet the growing demands of fish in the American diet, would remove a huge burden on our natural wildlife resources and would also reduce our dependence on imports.
Previously, open ponds were developed for use in aquaculture. These earthen ponds were scalable and required relatively small initial capital expenditures to construct, but required large land masses, were inefficient because of the ratio of square footage and consumptive gallons of water required per unit produced. Additionally the growing conditions and water quality in these ponds was difficult to monitor and control, harvesting was hit or miss, diseases were common and solid waste products and particulates were difficult to remove. Today, fresh water is becoming a rare commodity and there is an increasing need for more efficient usage of both land and water resources.
The current cutting edge technology for aquaculture in the United States employ round tanks that are provided with extensive pipe systems to provide fresh water and oxygen. Each of these tanks is equipped with fish feeders, control and monitoring equipment to continuously check water quality, water flow, dissolved gas content of the water and other parameters that would affect fish growth.
These tanks require a high level of maintenance which includes frequent manual removal of dead fish to minimize the incidence of disease within the confines of the tank. Upon death, fish will first sink to the bottom of the tank, then within the first 24 hours, plus or minus 2 to 4 hours depending upon water temperature and decomposition rates, will float to the surface. Thereafter, the carcass will continue to float on the surface waters of the tank where it will continue to decompose and serve as an incubator for disease causing organisms. The process of decay also produces by-products such as nitrogen compounds which adversely affect the water quality within the tank. This necessitates continuous monitoring and immediate removal of dead and dying fish.
Additionally, the size of the fish held within the tank must be kept relatively uniform to reduce the incidence of cannibalism in the fish population. The fish sorting required to maintain the sizing restrictions often requires mechanical or physical handling and relocation of the fish resulting in stress and trauma which can adversely affect the mortality, overall health and growth rate of the fish.
The harvesting of fish from such facilities is usually accomplished in much the same manner as harvesting of fish has occurred for centuries, use of nets for physical removal from the tank. This method is often less than efficient and may result in additional stress and physical damage to the fish during harvesting.
The round shape of these tanks provides an uneven current speed within the tank. Water on the outer perimeter of the tank is propelled at a higher rate of speed than the water in the center of the tank. Each species of fish prefers a particular rate of speed of water resulting in a sizeable percentage of the tank having a flow rate that will not be suitable for optimal fish habitat. If the water flow is slowed to provide for optimal fish habitat in the outer perimeter of the tank, the particulates in the water may settle to the bottom of the tank where removal of such particulate matter would require additional mechanical means of removal.
The current technology is very expensive to build and maintain, and becomes even more labor intensive and costly as the number of tank units increase. Round tanks are not readily scalable to larger systems because of the inherent problems in flow rate differentials and water mixing (as discussed below). This limits the diameter-to-depth ratio of round tanks to about 10:1. Since water depths are typically 5 feet or less for practical considerations (fish management, personnel safety, and construction cost), the effective maximum diameter of round tanks is about 50 feet. This has become a significant problem in constructing economically efficient large fish farms. The extreme number of round tanks required for large-scale fish production is counter-productive as they result in increased operational costs and no construction savings, on a cost-per-pound of fish produced basis. As effective as round tanks can be for small niche aquatic businesses or research systems, they do not offer the economy-of-scale opportunities necessary in the competitive environment of large-scale commercial aquaculture.
The concept of, and methods for aquacultural fish raising are well known and documented. Examples of different types of devices, methods and systems, water treatment units and techniques that might be suitable for aquaculture are disclosed in U.S. Pat. Nos. 6,382,134 B1, 6,192,833, 5,961,831, 4,915,059, 4,913,093, 4,516,528 and 4,300,477.
Fish rearing systems utilizing recycled water as a means of maintaining an aquaculture system have been explored. U.S. Pat. No. 6,382,134 B1 describes such a system. The system incorporates traps and screens for removal of particulate matter, denitrification devices, a disinfection device and ammonia treating devices. The system also incorporates an aeration device (for addition of oxygen and removal of carbon dioxide) and a means of monitoring water quality.
While this novel invention provides for means of removal of many of the gross particulates from the water by means of a trapping section at the bottom of the tank, it does not address the major problem of removal of dead and dying fish on a continuing basis. As previously mentioned, the dead or dying fish will sink to the bottom for the first 24 hour period after death, before floating to the top where they might be removed by mechanical means (with sunken dead fish potentially removed by the trapping section at the bottom of the tank). The presence of dead or dying fish represents a major potential source of disease which could affect the fish population in an entire system. Disinfection of a small portion of the water without prompt removal of the source of infection would not prevent the spread of the infection throughout the fish population due to physical contact with the decaying matter.
Prompt and continuous removal of dead and dying fish appears to offer the best preventative measure against widespread contamination and spreading of disease throughout a contained fish population. Therefore it would be highly desirable to have a new and improved scalable fish rearing raceway system and method of making same which would provide for continuous removal of dead fish from the raceway. The continuous mechanical removal of dead and dying fish significantly reduces labor costs associated with the frequent human monitoring and manual removal of such fish and reduces the transmittal of infectious diseases by the immediate removal of the dead and dying fish.
An aquaculture system which teaches a process or system for raising aquatic organisms is disclosed in U.S. Pat. No. 6,192,833. Therein, a system is provided that incorporates a raceway for producing and maintaining the organism and an algal growth channel with monitors and paddlewheel for flow control.
This system does not provide for means of particulate removal or removal of dead or dying fish. There is no means of providing for sizing of fish and, additionally, there is no provision for a harvesting channel. This novel invention does not provide for scalability of such a channel.
Therefore, it would be highly desirable to have a new and improved scalable fish rearing raceway system and method of making same for aquaculture products which would provide a sequential combination of subsystems for removal of the solid particulate matter as well as dead and dying fish. Furthermore, it would be highly desirable if such a system provided a separate channel or holding area for harvesting fish, moving fish to other tanks, and for uniform optional sizing of fish that can be incorporated into the raceway or channel, and which would be scalable.
The aquaculture system disclosed in U.S. Pat. No. 5,961,831 consists of one or more culture tanks connected to a closed system of filters and ultraviolet or ozone sources for water purification prior to returning water to the culture tanks. This invention also provides for sensors for continuous monitoring of water quality. However, as seen previously, there is no provision for removal of dead and dying fish which represents one of the most important potential reservoirs of disease within an aquaculture environment.
Therefore, it would be highly desirable to have a new and improved scalable fish rearing raceway system and method of making same which would provide for methods of particulate removal, but perhaps most importantly, provide for continuous mechanical removal of dead fish from the raceway by means of a floating mortality catcher consisting of screened ramps which collect moribund and dead fish, as well as a novel system for the prompt removal of freshly sunken dead fish.
As previously mentioned, many of the inventive systems utilized by aquaculture up until very recently have used multiple tanks for rearing of fish. Most of these systems were designed to utilize relatively small round tanks. Increasing the diameter of these small round tanks reveals inherent design restrictions that prevent efficient usage of the entire interior of the tank for rearing fish due to the centrifugal current differential within the confines of the circular space. Since increased tank diameter exacerbates the differential in water velocity within the tank, these large round tanks become inefficient in terms of space utilization. Additionally, the ability to scale them to a larger size would not be cost effective. Moreover, the space between the numerous tanks is essentially wasted space with respect to fish rearing operations.
The invention in U.S. Pat. No. 4,913,093 describes such a multi-tank aquaculture system. A method of culturing fish in a plurality of tanks with each tank comprising a relatively independent growing environment would require enormous capital and labor expenditures per fish produced. In addition, the invention requires periodic subdivision of the fish population into separate tanks when the capacity of the tank is reached. Physically sorting and moving the fish from tank to tank would result in a great deal of trauma and possibly injury to the fish.
Therefore, it would be highly desirable to have a new and improved scalable fish rearing raceway system and method of making same which would provide scalability, low capital expenditure, low labor cost per fish produced, efficient use of space, a means of separating fish by size, and a means by which those fish might be moved or harvested in an efficient manner without trauma or injury.
Another aquaculture rearing system is described in U.S. Pat. No. 4,300,477 which provides for clustered, vertical rearing tanks. Multiple, stackable habitats in the form of baskets are attached to a strongback member which houses a removable feeding rod. There is no means provided for removal of heavy particulates, dead or dying fish or providing for circulation of water through the tank.
Progressive space increments are provided by two different size baskets and removable dividers. The fact that these multiple habitats are individually removable suggests that the size of the baskets are relatively small and that the number of units of fish per basket is severely limited. This ratio of capital expenditure (and labor costs) per unit produced is extremely high. Additionally, the trauma involved in physical separation of the fish by size into each basket would be very high.
Additionally, there is no means provided for removal of dead or dying fish on a continuous basis, so the likelihood of spread of disease from the presence of dead or dying fish would seem to be overwhelming.
Therefore, it would be highly desirable to have a new and improved scalable fish rearing raceway system and method of making same which would provide a method by which particulates in the wastewater stream would be automatically removed. It would also be highly desirable to provide such a new and improved aquaculture raceway system with a means of providing fresh circulating oxygenated water, a water treatment process, and a means of removing dead and dying fish on a continuing basis. It would also be highly desirable to provide such fish sorting, removal of dead and dying fish, provision of fresh or reconditioned circulating water in a cost effective, efficient and scalable manner.
The present invention proposes a new and improved circular raceway for use in an aquaculture system and method of using same. The proposed raceway is easily scalable, is cost effective and efficient, and provides for more uniform water current velocities throughout the production tank.